Use of micellar solution as an emulsion breaker

ABSTRACT

Production of formation fluids through a well bore from a hydrocarbon-bearing subterranean formation having a water and hydrocarbon emulsion blockage surrounding the well bore is restored by injecting about 1 to about 500 gallons per vertical foot of hydrocarbon-bearing formation of micellar dispersion into the formation to &#39;&#39;&#39;&#39;solubilize&#39;&#39;&#39;&#39; the emulsion. The micellar dispersion is comprised of a surfactant having an average equivalent weight of 350-525.

United States Patent 1191 Webb 1 1*Mar. 26, 1974 USE OF MICELLAR SOLUTION AS AN 2,331,594 10/1943 Blair, .lr, 166/305 ux EMULSION BREAKER 2,356,205 8/1944 Blair, Jr. et al. 252/855 2,369,831 2/1945 Jones et al. 252/855 Inventor: Thomas Webb, Casper, y 3,185,217 5/1965 Brooks, Jr. et al. 166/305 x I 3,254,714 6/1966 Gogarty et al 166/274 [73] Asslgnee' 353 Company 3,402,770 9/1968 Messenger 166/305 R Notice: The portion of the term of this patent Subsequent to Jan. 12 193 Primary Examiner-Stephen J. Novosad has been disclaimed' Attorney, Agent, or Firm.loseph C. Herring; Richard C. Willson, Jr.; Jack L. l-lummel [22] Flled: Jan. 15, 1973 Appl. No.2 323,673

Related US. Application Data Division of Ser. No. 192,710, Nov. 9, 1971, which is a continuation-in-part of Ser. No. 762,140, Sept. 24, 1968, Pat. No. 3,554,289.

US. Cl 166/305 R Int. Cl E2lb 43/25 Field of Search 166/305 R, 273275;

References Cited UNITED STATES PATENTS l/1971 Webb 166/305 R 10 Claims, No Drawings USE OF MICELLAR SOLUTION AS AN EMULSION BREAKER CROSS REFERENCE TO RELATED APPLICATION This application is a divisional of my copending application Ser. No. 192,710, filed Nov. 9, 1971, which is a continuation-in-part of my copending application, Ser. No. 762,140, filed Sept. 24, 1968, now US. Pat. No. 3,554,289.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to removing water/hydrocarbon emulsion blocks from a producing well by solubilizing the emulsion with a micellar dispersion containing hydrocarbon, aqueous medium and surfactant.

2. Description of the Prior Art Production of oil and gas wells often experiences a sudden or gradual decrease in the production of hydrocarbon. In some cases, the hydrocarbon production may stop altogether. Such can be caused by an emulsion block in the hydrocarbon-bearing formation, i.e., a viscous emulsion of water and hydrocarbon is formed around the well bore and adversely affects the advance of hydrocarbon to the well bore.

The prior art teaches that surfactants suspended in a carrier, such as crude oil or water, are useful to overcome the emulsion blockage. Such a process has proved satisfactory in many cases.

In some cases, blockage is characteristic of a oneway emulsion blockage, i.e., fluid can be pumped without difficulty into the formation but when the formation is restored to production, the well will not produce. The so-called native emulsion is sometimes characteristic of this phenonemon.

Applicant has discovered that emulsion blockage in the formation can be removed by injecting a sufficient amount of a micellar dispersion into the formation to solubilize the emulsion. Once the emulsion is solubilized," the formation is returned to production. In creases in hydrocarbon production are realized. The term solubilization as used herein is broadly but not specifically meant to include take-up or partial take-up of the emulsion by emulsification or sorption by the micellar dispersion to substantially overcome the adversity imparted by the emulsion to the flow of hydrocarbon within the formation.

DESCRIPTION OF THE INVENTION The term micellar dispersion as used herein is meant to include micellar solutions, microemulsions transparent" emulsions (Blair, Jr. et al., US. Pat. No. 2,356,205), aqueous soluble oils and micellar solution technology taught in C. G. Sumner, Claytons The Theory 0f Emulsions and Their Technical Treatment, 5th Edition, pp. 315-320 1954). Specific examples of useful micellar solutions include those defined in US. Pat. Nos. 3,254,714 and 3,275,075 to Gogarty et al.; 3,307,628 to Sena and U. S. Pat. No. 3,497,006 to Jones et al. Micellar dispersions differ in many ways from emulsions, basically the micellar dispersion is thermodynamically stable and generally transparent whereas emulsions are not thermodynamically stable systems and are generally opaque.

The micellar dispersion is composed of hydrocarbon, aqueous medium, and surfactant. Cosurfactant(s) and electrolyte(s) can optionally be incorporated within the micellar dispersion. Examples of volume amounts include about 4 percent to about percent or more of hydrocarbon, about 10 percent to about percent aqueous medium, at least about 4 percent surfactant, about 0.01 to about 20 percent cosurfactant (also identified as cosolubilizer and semi-polar organic compound), and about 0.001 to about 5- percent or more (weight percent based on aqueous medium) of electrolyte. The micellar dispersion contains at least about 5 percent aqueous medium.

The micellar dispersion can be oil-external or waterexternal. Where the emulsion blockage is oil-external, it is preferred to use an oil-external micellar dispersion. However, where the emulsion blockage is waterexternal, a water-external micellar dispersion can be effectively used.

Examples of hydrocarbon useful in the micellar dispersion include crude oil, partially refined fractions of crude oil, refined fractions of crude oil, synthesized hydrocarbons, etc. Specific examples of such hydrocarbons include side cuts from crude columns, crude column overheads, gas oils, kerosenes, heavy naphthas, naphthas, straight-run gasoline, liquefied petroleum gases, propane, pentane, heptane, decane, dodecane, cyclohexane, aryl compounds, substituted aryl compounds, etc. Preferably, the hydrocarbon is one locally available and can be characteristic of the hydrocarbon within the particular formation being treated. Unsulfonated hydrocarbon within a petroleum sulfonate, e.g., unsulfonated gas oils, are useful as the hydrocarbon.

The aqueous medium can be soft, brackish, or brine water. When the aqueous medium contains ions, it is preferred that these ions be compatible or characteristic of the ions within the formation fluids.

Useful surfactants within the micellar dispersion include nonionic, cationic and anionic surfactantsjSpecific examples include those surfactants taught in US. Pat. No. 3,497,006, to Jones et al. Preferably, the surfactant is a petroleum sulfonate, also known as alkyl aryl naphthenic sulfonate. A-particularly useful sulfonate is a monovalent cation containing sulfonate, e.g., sodium and ammonium petroleum sulfonate. Preferably the petroleum sulfonate has an average equivalent weight within the range of about 350 to about 525 and more preferably about 390 to about 460. The surfactant can be a mixture of two or more of low, medium, and high average equivalent weight sulfonates or a mixture of two or more different surfactants.

The cosurfactant useful with this invention includes alcohols, amides, amino compounds, esters, aldehydes, ketones, and like materials containing from 1 to about 20 or more carbon atoms. Preferably, the cosurfactant contains about 3 to about 16 carbon atoms. Specific examples include alcohols such as isopropanol, nand iso-butanol, amyl alcohols such as n-amyl alcohol, 1- and 2hexanol, l-and 2-octanol, decyl alcohols, dodecyl alcohols, etc., and alkaryl alcohols such as pnonylphenol, alcoholic liquors such as fusel oil, compounds such as 2-butoxyethanol and like materials. Preferably, the cosurfactant is present in volume amounts of about 0.1 to about 5 percent. Mixtures of two or more cosurfactants are also useful.

Electrolytes useful within the micellar dispersion include inorganic salts, inorganic acids, inorganic bases, organic acids, organic bases and organic salts. Preferably, the electrolyte is compatible with the ions within the formation fluids. Specific examples of electrolytes include sodium hydroxide, sodium chloride, sodium sulfate, hydrochloric acid, sulfuric acid, and electrolytes taught in US. Pat. Nos. 3,330,343 to Tosch et a]. and 3,297,084 to Gogarty et al. Additionally, the electrolyte can be the salts or ions within the aqueous medium, e.g., within brine or brackish water. The type and concentration of electrolyte will depend on the aqueous medium, surfactant, cosurfactant, hydrocarbon, and the reservoir conditions, including temperature of the reservoir.

When the emulsion blockage contains a high ionic content, it is preferred that the micellar dispersion be designed to have a high affinity for brine. For example, the micellar dispersion can be designed with a lower average equivalent weight surfactant and/or a minimum amount of electrolyte--such can impart to the micellar dispersion a high brine affinity or a high solubilization potential for an emulsion containing a high brine content. Also, where the emulsion blockage is water-external, it may be desirable to design the micellar dispersion to be more water-like in character and to have a high affinity for the emulsion. However, where the emulsion blockage is oil-external, it may be desired to design the micellar dispersion to have a high affinity for hydrocarbon and thus the components within the micellar dispersion are chosen to impart a more oleophilic character to the micellar dispersion.

The amount of micellar dispersion injected into the formation should be sufficient to solubilize substantially the emulsion causing the emulsion blockage. Certain factors which will determine the amount of mice]- lar dispersion injected include: l) the permeability of the formation (where the formation is less permeable, it may be desired to inject more of the micellar dispersion), (2) porosity, i.e., where the porosity is large, a larger amount of micellar dispersion is required, etc. However, a volume about equal to or in excess of the volume of emulsion is about the maximum amount of micellar dispersion useful with the invention, from an economical basis. Generally, about 1 to about 500 gallons per vertical foot of hydrocarbon-bearing formation is useful to solubilize the emulsion.

After the micellar dispersion is injected into the formation, it is permitted to remain in contact for a sufficient period of time to solubilize the emulsion. Such time will vary with the particular formation, the volume and character of the emulsion, and the character of the micellar dispersion being injected. Examples of times include about 0.5 to about 24 hours.

Thereafter, the well is permitted to produce the formation fluids through the well bore. In restoring the well to production, the solubilized emulsion will be backflowed and thus removed uphole.

It is intended that the invention not be limited by the specific embodiments taught herein. Rather, all equivalents obvious to those skilled in the art are intended to be incorporated within the scope of this invention as defined within the specification and appended claims.

What is claimed is:

1. A method of restoring production of formation fluids from a hydrocarbon-bearing subterranean formation having a well bore penetrating the formation and wherein said formation is blocked by a water and hydrocarbon emulsion, the method comprising:

1. injecting about l to about 500 gallons of micellar dispersion per vertical foot of hydrocarbon-bearing formation into the formation, the micellar dispersion comprised of at least 5 percent aqueous medium and containing a surfactant having an average equivalent weight within the range of about 350 to about 525,

2. permitting the micellar dispersion to solubilize the emulsion and,

3. returning the well to production.

2. The method of claim 1 wherein the micellar dispersion is comprised of hydrocarbon, aqueous medium, and petroleum sulfonate.

3. The method of claim 2 wherein the micellar dispersion contains cosurfactant.

4. The method of claim 2 wherein the micellar dispersion contains electrolyte.

5. The method of claim 1 wherein the micellar dispersion is oil-external.

6. The method of claim 1 wherein the micellar dispersion is water-external.

7. A method of restoring production of formation fluids from a hydrocarbon-bearing subterranean formation having a well bore penetrating therein and wherein the formation is blocked by a water and hydrocarbon emulsion, the method comprising:

1. injecting into the formation about 1 to about 500 gallons per vertical foot of hydrocarbon-bearing formation ofa micellar dispersion comprised of hydrocarbon, petroleum sulfonate having an average equivalent weight of about 350 to about 525, and aqueous medium,

2. permitting the micellar dispersion to remain in the formation until the emulsion is substantially solubilized by the micellar dispersion, and

3. returning the well to production.

8. The method of claim 7 wherein the micellar dispersion contains cosurfactant.

9. The method of claim 7 wherein the micellar dispersion contains electrolyte.

10. The method of claim 7 wherein the micellar dispersion is oil-external. 

2. The method of claim 1 wherein the micellar dispersion is comprised of hydrocarbon, aqueous medium, and petroleum sulfonate.
 2. permitting the micellar dispersion to remain in the formation until the emulsion is substantially solubilized by the micellar dispersion, and
 2. permitting the micellar dispersion to solubIlize the emulsion and,
 3. returning the well to production.
 3. returning the well to production.
 3. The method of claim 2 wherein the micellar dispersion contains cosurfactant.
 4. The method of claim 2 wherein the micellar dispersion contains electrolyte.
 5. The method of claim 1 wherein the micellar dispersion is oil-external.
 6. The method of claim 1 wherein the micellar dispersion is water-external.
 7. A method of restoring production of formation fluids from a hydrocarbon-bearing subterranean formation having a well bore penetrating therein and wherein the formation is blocked by a water and hydrocarbon emulsion, the method comprising:
 8. The method of claim 7 wherein the micellar dispersion contains cosurfactant.
 9. The method of claim 7 wherein the micellar dispersion contains electrolyte.
 10. The method of claim 7 wherein the micellar dispersion is oil-external. 